Compact Sheetrock Saw

The origin of this project came about because I was looking for a very specific set of features that I was never able to find in a ready made unit

As an A/V (audio/visual) technician I frequently have to cut sheetrock to run wires and install wallplates. Since I mostly work on completed houses (retrofitting) rather than new construction and the walls are 2x4 construction there is no need to have a blade longer than 4 inches

I also wanted to be able to carry spare blades with the unit in case of breakage along with storage for the blade I'm using instead of needing a sheath

Space is always at a premium in my toolbox so it has to be small

Lastly I want the blade to be tightly held (some of the folding units have a lot of wiggle)

Step 1: The Parts

The parts list is pretty small

5 inches of 1/2 inch copper pipe

1 end cap for 1/2 inch copper pipe

1 5/8 compression union fitting (5/8 is the outside diameter of 1/2 inch pipe)

bar stock 3/4 inch diameter (I used aluminum but steel or brass is fine) , The finished piece is only about an inch long

1/4 keyway stock , Again the finished piece is only about an inch long

T shank jigsaw blade

Step 2: The Tools

Metal Lathe ( It's a very simple turning and you may be able to make it on a drill press if it has a big enough chuck)

Metal files ( I cut the 1/4 inch slot on a mill but a file is all that's really needed)

Bench vise

Propane torch and solder

Wrenches

Precision caliper (vernier, dial or digital)

Step 3: Construction

Measuring the union I got .630 thru the hole on the nut nut and .600 on the pass thru in the middle of the union ( I don't know how much tolerances there are between different manufacturers)

Turn the bar stock to the measured dimensions with approximately 1/4 inch on one end turned to the small dimension and the rest turned to just fit thru the hole in the nut (you will end up with a stepped shaft)

Cut the stepped end off of the bar stock (my finished length was .915) , when assembled we want it to just pass thru the hole in the nut and protrude a little. We also want to put a bit of a champfer on the end that passes thru the nut for ease of assembly.

Mill (or file) a slot in the bar stock 1/4 inch wide and just less than 1/4 inch deep. Using a blade as a guide file a cross slot in the bar stock the same depth as the 1/4 inch slot

Using the key stock cut a piece of a little bit shorter than the bar stock (my finished dimension was .685) . using a file we want to curve the top of the key stock and put a taper on the ends so the taper in the nut and union will make it wedge against the blade and bushing causing it to lock everything up tight when the nut is tightened (this took me two tries to get it right) . This part requires hand fitting and a little patience to get it right, the advantage of doing it this way is it will automatically compensate for difference in blade thickness and lock up tight with no wiggle in the blade.

I filed a second cross slot near the back of the bar stock to allow flipping the blade over for storage (if there isn't a blade in the slot the wedge can't tighten and everything falls out of the end)

Step 4: Assembly

Solder the end cap on one end of the copper pipe

Install one end of the union onto the other end of the pipe and tighten

Spare blades are passed thru the union into the handle for storage

Install the bar stock bushing ,blade, and wedge into the other end of the union (the brass bead isn't used)

Install nut and tighten ( I've only had to hand tighten and haven't had it loosen but you can always use a wrench if you want it extra tight)

While I have never hit a live wire in a wall this unit is all metal and should be wrapped with a couple of layers of friction or plastic tape for insulation for safety's sake.